180 



spicuous air cavities, while the cortex of the nonaerated root (Fig. 3) 

 contained large air cavities separated by narrow strands of tissue. 



This experiment shows the great importance of the presence of air 

 not only for the normal growth of plant tissue but also the obtaining 

 of the maximum plant growth. 



The woi'k of which this study is the result was taken up at the 

 suggestion of Prof. Andrews of the Department of Plant Physiology 

 of Indiana University, and his constant interest and help have con- 

 tributed to its completion. 



